The invention relates to a new catalyst composition useful for initiating and promoting polymerization of one or more .alpha.-olefins and to a polymerization process employing such a catalyst composition.
Fuentes, Jr. and Esneault disclosed in U.S. Pat. Nos. 4,526,943 and 4,544,647 the polymerization of .alpha.-olefins employing a high yield catalyst. This high yield catalyst was prepared from an organomagnesium material, an organic hydroxyl-containing material, a reducing halide source and a transition metal compound. While this catalyst prepared polymers in high yield, it would be desirous if polymers could be produced with varying particle sizes. The present invention provides a method for producing polymers with varying particle sizes. It is desirable to have polymers produced in varying particle sizes because in some instances such as when an .alpha.-olefin polymer is to be chemically modified while still in the powder form, it is desirable to present as small a particle size as possible in order to present a large surface area for modification. It is also sometimes desirable to have a small average particle size when efficient removal of the inert polymerization diluent from the .alpha.-olefin polymer is required. In some instances in which extrusion processing the polymer is not performed, it is desirable to have as large a particle size as possible for improved handling of the .alpha.-olefin polymer.
The present invention provides a method for preparing polymers in various and controlled particle sizes by employing in the catalyst formulation an inorganic oxide of various particle sizes. The particle size of the resultant particle varies with the particle size of the inorganic oxide. An additional advantage of the present invention is that no activation or special preparation of the inorganic oxide is required before its use in the preparation of the catalyst. In most instances with catalysts prepared using as a component of their formulation an inorganic oxide, the inorganic oxide must first be calcined, or heat treated, in order to remove water and activate the surface of the inorganic oxide.